i have a rover 75 2002 auto out of the blue sunday it would not start?

i have had it in the garage for 3 days they cant find why it has fuel it has spark but it seems the injectors either arnt geting enough or the pressures not enough to open injectors . i have already spent £200 on changing the sensors to see if its this works but still the same . if they put petrol straight into fuel pipe on the engine it starts but wont tick over then that fuel runs out and it dies again and wont restart ????? please help as we are running out of ideas